#include<stdio.h>
int main()
{
	int i = 0;
	int flag = 1;
	float sum = 0;
	for (i = 1; i <= 100; i++)
	{
		sum = sum + flag*(1.0 / i);
		flag = -flag;
	}
	printf("%f\n", sum);
	return 0;
}